1. Field of the Invention
The present invention relates to a tape-type magnetic recording medium adaptable to a yoke-type magnetoresistance effect magnetic head using a magnetoresistance effect device, and to a method of reproducing a signal from the tape-type magnetic recording medium by using the yoke-type magnetoresistance effect magnetic head.
2. Description of Prior Art
Since a quantity of information which must be recorded has been enlarged, a rise in the recording density has been strongly required in the magnetic recording field. Therefore, a so-called thin-film type magnetic recording medium has mainly been employed in place of a so-called coating-type magnetic recording medium containing magnetic particles dispersed in the binder thereof. The thin-film type magnetic recording medium has a structure that ferromagnetic metal is formed into a film by plating or by using a means for forming a thin film in a vacuum state (a vacuum evaporation method, a sputtering method, an ion plating method or the like).
The thin-film type magnetic recording medium obtained by forming the ferromagnetic metal into a film exhibits large coercive force and excellent square ratio. Moreover, the foregoing medium is not required to mix a binder, which is a non-magnetic material, into the magnetic layer as has been required for the coating-type magnetic recording medium. Therefore, the density at which the magnetic material is filled (that is, the quantity of magnetization per unit volume) can be raised. The thickness of the magnetic layer of the thin-film type magnetic recording medium can considerably be reduced as compared with that of the coating-type magnetic recording medium. Therefore, the thin-film type magnetic recording medium exhibits excellent electromagnetic conversion characteristic in a short wavelength region. Moreover, the thin-film type magnetic recording medium has a characteristic that demagnetization occurring during the recording operation can significantly be reduced. Since the thin-film type magnetic recording medium has the above-mentioned advantageous characteristics as compared with the coating-type magnetic recording medium, it is expected to become a major portion of magnetic recording mediums capable of recording signals at a high density.
In the above-mentioned magnetic recording field, a tape-type magnetic recording medium has been employed which has a magnetic layer formed by a diagonal evaporation method. The tape-type magnetic recording medium formed by the diagonal evaporation method is formed in such a manner that the magnetic layer is formed on a moving non-magnetic support member (in the form of a polyester film or a polymer film made of polyamide or a polyamide film) by diagonally depositing magnetic metal by the vacuum evaporation method. The tape-type magnetic recording medium manufactured by the diagonal evaporation method has a structure that magnetic particles are oriented diagonally with respect to the surface of the non-magnetic support member. Thus, a denser recording operation can be performed as compared with the conventional magnetic tape in which magnetic particles are oriented in the lengthwise direction of the magnetic tape. Specifically, the thin-film type magnetic recording medium has a structure that the magnetic layer has an axis of easy magnetization which is inclined by about 20.degree. with respect to the surface of the non-magnetic support member.
To meet the requirement for raising the recording density, the magnetic head must be improved as well as the improvement in the magnetic recording medium. In particular, a reproducing method has received attention which employs a yoke-type magnetoresistance effect magnetic head (hereinafter called a "yoke type MR head").
The yoke type MR head is a magnetic head using a magnetoresistance effect and capable of detecting a weaker magnetic field of a signal. Therefore, the yoke type MR head 10 can be used even if the magnetic field of the signal is reduced when the recording wavelength is shortened because of the dense recording operation.
However, when the tape-type magnetic recording medium is reproduced by using the yoke type MR head 10, optimum conditions have not been considered. As a result, a satisfactorily high recording density has not been realized.